| 摘要 |
<p>1334059 Monitoring pulse trains; radio signalling RCA CORPORATION 18 Dec 1970 [29 Dec 1969] 60159/70 Headings H3A and H4L A circuit monitoring a train of random pulses comprises a bi-stable set to one state by the random pulses and set to the other state by regularly recurring pulses of longer duration, the output of the bi-stable being fed to an average detector. Composite stereo signals from a tuner 12, and a 114 kHz signal from source 18 are fed to a noise detector 16 which translates noise of the composite signal, lying in the region of 114 kHz, down to a low frequency band which is fed via adjustable low pass filter 40, 42, 44 to a threshold circuit 46, 48, 50. If the amplitude of this signal exceeds that of threshold source 52, it is passed to the set input of a bistable 66, 68, which receives as its reset input, a signal from source 84. As long as noise signals are present at the bi-stable set input, the bistable will switch to produce a pulse output signal which allows capacitor 64 to discharge and operate switch 62. The output from the noise detector automatically adjusts itself to allow more noise in loud music passages before switching occurs.</p> |
